The present invention relates to a compressor, and more particularly to a plurality of end-wall treatments disposed in a casing and/or a hub of such compressor.
Compressors used in engines such as a gas turbine, may include a plurality of stages arranged along a length of the compressor. Each stage may include a hub and a plurality of rotor blades arranged about a circumference of the hub. In addition, each stage may further include a plurality of stator blades, disposed alternately to the plurality of rotor blades and arranged about a circumference of a casing of the compressor.
During operation of such gas turbine, the hub of the compressor may be rotated at high speed by a turbine, such that a fluid is continuously induced into the compressor. The fluid is accelerated by the rotating rotor blades and swept rearwards onto the adjacent rows of the stator blades. At each stage, the rotor blade and/or stator blade increases pressure of the fluid. In addition, during operation of the compressor, a portion of the fluid may flow about a tip of each rotor blade and/or stator blade as a leakage flow. Such stage-to-stage leakage of compressed fluid as the leakage flow affects the stable operating range of the compressor and adversely affects the efficiency of the gas turbine. The point at which the compressor starts operating in an unstable condition may be referred to as the stall point of the compressor.
The operating range of the compressor is generally limited due to weak flow at the tip of the blade. Prior attempts to increase the operating range and improve the stall margin have included flow control based techniques such as plasma actuation and suction/blowing near a blade tip. However, such attempts may significantly increase complexity and weight of the compressor. Other attempts include end-wall treatments such as circumferential grooves, axial grooves, and the like. Early attempts on such end-wall treatments have a substantial impact on design point efficiency with very minimal benefit in improving the stall margin of the compressor.
Thus, there is a need for an improved end-wall treatment for a compressor and an associated method for controlling a leakage flow about one or more blade tips and thereby improving a stall margin of the compressor.